Hundreds of schools in Northern Ireland, Scotland, Hungary and Serbia were sent bomb threats on Monday with some evacuated as authorities said the warnings appeared to be a hoax. It is not yet known whether the incidents were connected to each other.

“Police investigating the circumstances of threatening emails sent to schools across Northern Ireland this morning … are treating the matter as a hoax,” police said.

Northern Ireland police said up to 300 schools had received “the same emailed message which contained a generalised threat” which was also received by “some schools across the UK”.

Earlier on Monday, Northern Ireland Education Minister Paul Givan said the emails appeared to be “from Islamists threatening that sharia law will be brought into our country and that there are viable devices within those school settings”.

Givan said the email was signed off “Allahu akbar”, meaning “God is great” and some schools had closed as a result.

“I want to absolutely condemn the actions of those who sought to disrupt our education system today by issuing threatening emails to our schools,” Givan added.

Meanwhile, Scottish police said “threatening messages” had also been sent to “a number of schools across Scotland”.

“These are being treated as a hoax and officers are investigating,” Police Scotland said in a statement.

In central Europe, Hungary saw emails sent to local media, claiming that bombs had been placed in more than 70 schools across the country, according to police. Many of the establishments were evacuated, but officials said no bombs were found.

“Based on the investigations carried out so far, this morning’s threats have proved to be unfounded,” Hungary’s interior minister Gabor Posfai said on In neighbouring Serbia, state broadcaster RTS reported that more than 100 schools had also received bomb threats.

The nature of the messages outside Northern Ireland remained unclear, and the Northern Irish education authority said in a statement that “the majority of schools remained open”.